1. Field of the Invention
The present invention relates to an information transmitting apparatus, an information receiving apparatus and an information transmitting/receiving apparatus, which are included in an information transmitting system, in which a serial bus is used to connect a plurality of apparatuses and information is transmitted between the apparatuses.
2. Description of the Related Art
Recently, a so-called IEEE 1394 standard (whose nominal name is xe2x80x9cIEEE (institute of Electrical and Electrical Engineers) Std.1394-1995 IEEE Standard for a High Performance Serial Busxe2x80x9d) is published as a new standard to transmit information in real time through a serial bus between a plurality of information apparatuses (for example, a personal computer, a digital video camera, an MD (Mini Disk) and the like). A digital video camera, a personal computer and the like having a serial port based on this standard are manufactured.
This IEEE 1394 standard is standardized such that a plurality of information apparatuses (hereafter, merely referred to as xe2x80x9cnodesxe2x80x9d) are connected through a serial bus to each other, and the information corresponding to a plurality of channels are transmitted in time sharing between these respective nodes (in this standard, it is standardized that the information can be transmitted by using a maximum of 63 different channels within a system connected through the serial bus).
In the IEEE 1394 standard, the initialization of a serial bus referred to as a so-called bus reset is standardized if another information apparatus is newly connected to a group of information apparatuses which are already connected through the serial bus to each other (namely, at a time of bus connection), or if one information apparatus is removed from the group of information apparatuses (namely, at a time of bus disconnection). Then, the following processes are carried out in conjunction with the bus reset, and a new connection manner is established (hereafter, this connection manner is referred to as a xe2x80x9ctopologyxe2x80x9d).
(1) In conjunction with an occurrence of the bus reset, a node which has detected the occurrence of the bus reset (namely, a node to which an information apparatus is newly connected or a node from which a previous connection is separated) sends a bus reset signal indicative of the occurrence of the bus reset to all nodes connected to the serial bus.
(2) After the bus reset, a tree identification is carried out to connect each node onto a tree. Then, a node located at a vertex of the connected tree is recognized as a route node.
(3) Then, the recognized route node instructs each node to recognize an identification number (ID number) peculiar to each node to identify each node within a tree system.
(4) An IRM (Isochronous Resource Manager) node is set, which serves as a node for managing the communication statuses (actually, use channels of the respective nodes and later-described transmission occupation periods) of all the nodes within the generated tree and which is displayed by other nodes at an identifiable manner.
(5) Finally, a bus manager node is set, which serves as a node for controlling the information transmission statuses of all the nodes is established.
A new topology after the bus reset is established by the processes at the above-mentioned five stages.
If the information is actually transmitted after the establishment of the topology, a transmitting node serving as a node to start the transmission of the information inquires of the IRM node the current communication statuses at the other nodes. If a transmission occupation period and a channel which the transmitting node desires to use are available, the transmitting node obtains a right of transmitting the information and starts the transmission of the information.
Next, the transmission occupation period will be schematically described below.
In the IEEE 1394 standard the information from each node is collectively transmitted for each information unit, referred to as an isochronous cycle. This isochronous cycle includes an isochronous transmission area which contains information to be transmitted synchronously with the information contained in the other isochronous cycles, and an asynchronous transmission area which contains information to be transmitted asynchronously with and independently of the other information. The information within the isochronous transmission area is time-shared for each channel, so that different information is transmitted for each channel.
At this time, in the isochronous transmission area, it is standardized that a length of the isochronous transmission area within one isochronous cycle has a maximum of 100 xcexcsec. Thus, it is necessary that a total of periods occupied by the information assigned to the respective channels within one isochronous transmission area for the transmission is equal to or less than 100 xcexcsec. At this time, the transmission time occupied by one channel within the isochronous cycle is the above-mentioned transmission occupation period. In addition, this transmission occupation period may be referred to as a use band of a serial bus, or may be referred to as a use capacity of a serial bus depending on a case. Also, when a length of the isochronous transmission area is less than 100 xcexcsec (including a case of zero) within one isochronous cycle, an area within the isochronous cycle other than the isochronous transmission area is exclusively used as the asynchronous transmission area.
By the way, it is standardized that in the serial buses connected to each other, if the bus reset is induced by the disconnection or connection of the bus during the transmission of the information, the transmission occupation period and the channel can be successively each node by the after the bus reset, which have been used before the bus reset.
In this case, for example, as shown in FIG. 14A, while information is transmitted from a node 100 through a serial bus 103 to a node 101 by using a channel 1, if a node 102 is newly connected through a serial bus 104 to the node 101, although a new topology is established after the bus reset, the information transmission can be continued between the node 100 and the node 101 and between the node 101 and the node 102 without any problem, as the node 102 uses a different channel 2 to transmit the information to the node 101 for example.
However, for example, as shown in FIG. 14B, while information is transmitted from a node 105 through a serial bus 109 to a node 106 by using the channel 1 and also while information is transmitted from a node 108 through a serial bus 110 to a node 107 by using the channel 1, if the node 106 and the node 108 are connected to each other through a serial bus 111 to thereby induce a bus reset, it is recognized on the standard that the transmission of the information is continued by using the same channel 1 as that before the bus reset, as for the node 105, as mentioned above. At the same time, it is also recognized on the standard that the transmission of the information is continued by using the same channel 1 as that before the bus reset, as for the node 108.
When this situation is considered from the standpoint of the node 107, the node 107 can receive both the information transmitted by the node 105 and the information transmitted by the node 108 on the topology. However, in this case, both are transmitted by using the same channel 1. Thus, the mixture of both the information is transmitted to the node 107.
Here, in the IEEE 1394 standard, the node of receiving information (the node 107, in the case of FIG. 14B) is allowed to only select a reception channel. Thus, in the case shown in FIG. 14B, the node 107 cannot judge whether it receives the information from the node 105 or receives the information from the node 108. This results in a problem that the node 107 cannot normally receive the information.
On the other hand, when a transmission occupation period of the information transmitted by the node 105 and a transmission occupation period of the information transmitted by the node 108 are considered in the case shown in FIG. 14B, they transmit the information independently of each other until the node 106 and the node 108 are connected to each other. Thus, the respective transmission occupation periods have no relation to each other.
However, in this case, the establishment of the connection between the node 106 and the node 108 causes the bus reset to be induced, which may cause a new topology to be established. Then, even after the bus reset, the node 105 and the node 108 try to transmit the information under the same channels and transmission occupation periods as those before the bus reset. Thus, there may be a case that the sum of the transmission occupation period of the information transmitted by the node 105 and the transmission occupation period of the information transmitted by the node 108 exceeds 100 xcexcsec which is allowed on the standard, after the bus reset.
In this case, the transmission occupation period as the entire isochronous transmission area within the above-mentioned isochronous cycle exceeds 100 xcexcsec. Thus, this case cannot meet the IEEE 1394 standard. This results in a problem that there may be a case in which the normal transmission of the information cannot be carried out.
The present invention is proposed in view of the above mentioned problems. It is therefore an object of the present invention to provide an information transmitting apparatus, an information transmitting method, an information receiving apparatus, an information receiving method, an information transmitting/receiving apparatus and an information transmitting/receiving method, in which even if a bus reset is induced in an entire new information transmitting system established by a connection of a plurality of information transmitting systems each independently transmitting information under the IEEE 1394 standard, the information can be normally transmitted between at least two nodes after the bus reset.
The above object of the present invention can be achieved by an information transmitting apparatus, which is included in a system for transmitting information through a bus such as a serial bus etc., for transmitting the information onto the bus. The information transmitting apparatus is provided with: an initialization detecting device such as a controller etc., for detecting whether or not the bus is initialized; an obtaining device such as a packet receiving unit etc., for obtaining post-initialization information, which is the information transmitted on the bus immediately after an initialization of the bus when the initialization of the bus is detected by the initialization detecting device; and a transmission controlling device such as a transmission judging circuit etc., for judging whether or not transmission information, which is the information to be transmitted onto the bus, can be transmitted in accordance with the obtained post-initialization information, and then transmitting the transmission information onto the bus if it is judged that the transmission information can be transmitted.
According to the information transmitting apparatus of the present invention, since it is judged whether or not the transmission information can be transmitted in accordance with the post-initialization information which is firstly transmitted on the bus after the initialization of the bus, it is possible to perform the transmission of the transmission information from at least one information transmitting apparatus when a plurality of different transmission informations are to be transmitted onto the bus from a plurality of information transmitting apparatuses each having the above described structure.
Therefore, it is possible to maintain the continuity of the information transmission from at least one information transmitting apparatus even after the bus is initialized.
In one aspect of the information transmitting apparatus of the present invention, the information transmitting apparatus is further provided with: a channel judging device such as a channel judging circuit etc., for judging whether or not a use channel, which is a channel used by the transmission information, is already used by the post-initialization information on the bus in accordance with the obtained post-initialization information; an occupied period detecting device such as an occupied period measuring circuit etc., for detecting a transmission occupied period, which is a period occupied while the post-initialization information is transmitted on the bus, in accordance with the obtained post-initialization information; and an occupied period judging device such as an occupied period judging circuit etc., for judging whether or not an occupied period sum, which is a sum of the detected transmission occupation period and the transmission occupation period corresponding to the transmission information, is shorter than a predetermined allowable period based on a performance of the bus. The transmission controlling device transmits the transmission information onto the bus, if the use channel is not used by the post-initialization information and further the occupation period sum is shorter than the predetermined allowable time, in accordance with a judgment result of the channel judging device and a judgment result of the occupied period judging device.
According to this aspect, since the transmission of the transmission information is performed when the use channel which is tried to be used by the transmission information is not already used and the occupation period sum including the transmission occupied period corresponding to the transmission information is shorter than the predetermined allowable time, it is possible to prevent a plurality of different transmission informations from being mixed on one channel, and can also prevent a transmission occupied period out of the standard from being generated.
In this aspect, the system may include a managing device such as an IRM node. etc, which manages the channel presently used within the system and the transmission occupied period presently occupied. The transmission controlling device may control the managing device to manage the transmission occupied period and the use channel corresponding to the transmission information if the use channel is not used by the post-initialization information and further the occupation period sum is shorter than the predetermined allowable time, in accordance with the judgment result of the channel judging device and the judgment result of the occupied period judging device.
By constructing in this manner, it is possible to make each apparatus, which is included in the system, speedily recognize the use channel used by the transmission information and the transmission occupied period occupied by the transmission information.
The above object of the present invention can be also achieved by an information receiving apparatus, which is included in a system for transmitting information through a bus such as a serial bus etc. for receiving the information transmitted by the above described information transmitting apparatus of the present invention. The information receiving apparatus is provided with: a second initialization detecting device such as a controller etc., for detecting whether or not the bus is initialized; a continuity detecting device such as a DBC (Data Block Counter) judging circuit etc., for receiving the post-initialization information when the bus is initialized according to a detection result of the second initialization detecting device, and detecting a presence or absence of a continuity between the information received before the initialization and the post-initialization information; and a demodulating device such as a packet selecting circuit etc., for determining that the received post-initialization information is the transmission information only if there is the continuity according to a detection result of the continuity detecting device, and then demodulating the received post-initialization information.
According to the information receiving apparatus of the present invention, when receiving the transmission information transmitted by the information transmitting apparatus of the present invention, since it is judged whether the receiving and decoding operations are to be carried out or not by detecting the presence or absence of the continuity of the information before and after the bus initialization, it is possible to successively receive and decode the information, which has been received until that time, even if the bus is initialized.
Therefore, it is possible to continue the information transmission between the information transmitting apparatus and the information receiving apparatus of the present invention even after the bus initialization.
In one aspect of the information receiving apparatus of the present invention, the continuity detecting device detects order information, which is included in an information unit in the post-initialization information and indicates an order of the information unit in the post-initialization information, and detects the continuity if there is a continuity between the order information in the information received before the initialization and the order information in the post-initialization information.
According to this aspect, since the continuity of the information before and after the bus initialization is detected by use of the continuity of the order information included in the information unit of the post-initialization information, it is possible to certainly receive the information continued before and after the bus initialization.
The above object of the present invention can be also achieved by an information transmitting/receiving apparatus, which is included in a system for transmitting information through a bus, provided with the above described information transmitting apparatus of the present invention, and an information receiving apparatus for receiving the information transmitted onto the bus by the information transmitting apparatus. The information receiving apparatus is provided with: a continuity detecting device for receiving the post-initialization information when the bus is initialized according to a detection result of the second initialization detecting device, and detecting a presence or absence of a continuity between the information received before the initialization and the post-initialization information; and a demodulating device for determining that the received post-initialization information is the transmission information only if there is the continuity according to a detection result of the continuity detecting device, and then demodulating the received post-initialization information.
According to the information transmitting/receiving apparatus of the present invention, since it is provided with the above described information transmitting apparatus of the present invention, it is possible to perform the transmission of the transmission information from at least one information transmitting apparatus when a plurality of different transmission informations are to be transmitted onto the bus from a plurality of information transmitting apparatuses each having the above described structure. Further, since, when receiving the transmission information transmitted by the information transmitting apparatus of the present invention, it is judged whether the receiving and decoding operations are to be carried out or not by detecting the presence or absence of the continuity of the information before and after the bus initialization, it is possible to successively receive and decode the information, which has been received until that time, even if the bus is initialized.
In one aspect of the information transmitting/receiving apparatus of the present invention, the information transmitting apparatus is further provided with: a channel judging device for judging whether or not a use channel, which is a channel used by the transmission information, is already used by the post-initialization information on the bus in accordance with the obtained post-initialization information; an occupied period detecting device for detecting a transmission occupied period, which is a period occupied while the post-initialization information is transmitted on the bus, in accordance with the obtained post-initialization information; and an occupied period judging device for judging whether or not an occupied period sum, which is a sum of the detected transmission occupation period and the transmission occupation period corresponding to the transmission information, is shorter than a predetermined allowable period based on a performance of the bus. The transmission controlling device transmits the transmission information onto the bus, if the use channel is not used by the post-initialization information and further the occupation period sum is shorter than the predetermined allowable time, in accordance with a judgment result of the channel judging device and a judgment result of the occupied period judging device.
According to this aspect, since the transmission of the transmission information is performed when the use channel which is tried to be used by the transmission information is not already used and the occupation period sum including the transmission occupied period corresponding to the transmission information is shorter than the predetermined allowable time, it is possible to prevent a plurality of different transmission informations from being mixed on one channel, and can also prevent a transmission occupied period out of the standard from being generated.
The above object of the present invention can be also achieved by an information transmitting method, in a system for transmitting information through a bus, of transmitting the information, onto the bus. The information transmitting method includes: an initialization detecting process of detecting whether or not the bus is initialized; an obtaining process of obtaining post-initialization information, which is the information transmitted on the bus immediately after an initialization of the bus when the initialization of the bus is detected by the initialization detecting process; and a transmission controlling process of judging whether or not transmission information, which is the information to be transmitted onto the bus, can be transmitted in accordance with the obtained post-initialization information, and then transmitting the transmission information onto the bus if it is judged that the transmission information can be transmitted.
According to the information transmitting method of the present invention, in the same manner as the above described information transmitting apparatus of the present invention, it is possible to perform the transmission of the transmission information from at least one information transmitting apparatus when a plurality of different transmission informations are to be transmitted onto the bus from a plurality of information transmitting apparatuses each having the above described structure.
In one aspect of the information transmitting method of the present invention, the information transmitting method further includes: a channel judging process of judging whether or not a use channel, which is a channel used by the transmission information, is already used by the post-initialization information on the bus in accordance with the obtained post-initialization information; an occupied period detecting process of detecting a transmission occupied period, which is a period occupied while the post-initialization information is transmitted on the bus, in accordance with the obtained post-initialization information; and an occupied period judging process of judging whether or not an occupied period sum, which is a sum of the detected transmission occupation period and the transmission occupation period corresponding to the transmission information, is shorter than a predetermined allowable period based on a performance of the bus. The transmission controlling process transmits the transmission information onto the bus, if the use channel is not used by the post-initialization information and further the occupation period sum is shorter than the predetermined allowable time, in accordance with a judgment result of the channel judging process and a judgment result of the occupied period judging process.
According to this aspect, in the same manner as the above described one aspect of the information transmitting apparatus of the present invention, it is possible to prevent a plurality of different transmission informations from being mixed on one channel, and can also prevent a transmission occupied period out of the standard from being generated.
In this aspect, the system may include a managing device such as an IRM node. etc, which manages the channel presently used within the system and the transmission occupied period presently occupied. The information transmitting method may control the managing device to manage the transmission occupied period and the use channel corresponding to the transmission information if the use channel is not used by the post-initialization information and further the occupation period sum is shorter than the predetermined allowable time, in accordance with the judgment result of the channel judging process and the judgment result of the occupied period judging process.
By constructing in this manner, it is possible to make each apparatus, which is included in the system, speedily recognize the use channel used by the transmission information and the transmission occupied period occupied by the transmission information.
The above object of the present invention can be also achieved by an information receiving method, in a system for transmitting information through a bus, of receiving the information transmitted by the above described information transmitting method of the present invention. The information receiving method includes: a second initialization detecting process of detecting whether or not the bus is initialized; a continuity detecting process of receiving the post-initialization information when the bus is initialized according to a detection result of the second initialization detecting process, and detecting a presence or absence of a continuity between the information received before the initialization and the post-initialization information; and a demodulating process of determining that the received post-initialization information is the transmission information only if there is the continuity according to a detection result of the continuity detecting process, and then demodulating the received post-initialization information.
According to the information receiving method of the present invention, in the same manner as the above described information receiving apparatus of the present invention, it is possible to successively receive and decode the information, which has been received until that time, even if the bus is initialized.
In one aspect of the information receiving method of the present invention, the continuity detecting process detects order information, which is included in an information unit in the post-initialization information and indicates an order of the information unit in the post-initialization information, and detects the continuity if there is a continuity between the order information in the information received before the initialization and the order information in the post-initialization information.
According to this aspect, in the same manner as the above described one aspect of the information receiving apparatus of the present invention, it is possible to certainly receive the information continued before and after the bus initialization.
The above object of the present invention can be also achieved by an information transmitting/receiving method, in a system for transmitting information through a bus, including the above described information transmitting method of the present invention and an information receiving method of receiving the information transmitted onto the bus by the information transmitting method. The information receiving method includes: a continuity detecting process of receiving the post-initialization information when the bus is initialized according to a detection result of the second initialization detecting process, and detecting a presence or absence of a continuity between the information received before the initialization and the post-initialization information; and a demodulating process of determining that the received post-initialization information is the transmission information only if there is the continuity according to a detection result of the continuity detecting process, and then demodulating the received post-initialization information.
According to the information transmitting/receiving method of the present invention, in the same manner as the above described information transmitting/receiving apparatus of the present invention, it is possible to perform the transmission of the transmission information from at least one information transmitting apparatus when a plurality of different transmission informations are to be transmitted onto the bus from a plurality of information transmitting apparatuses each having the above described structure. Further, it is possible to successively receive and decode the information, which has been received until that time, even if the bus is initialized.
In one aspect of the information transmitting/receiving method of the present invention, the information transmitting method further includes: a channel judging process of judging whether or not a use channel, which is a channel used by the transmission information, is already used by the post-initialization information on the bus in accordance with the obtained post-initialization information; an occupied period detecting process of detecting a transmission occupied period, which is a period occupied while the post-initialization information is transmitted on the bus, in accordance with the obtained post-initialization information; and an occupied period judging process of judging whether or not an occupied period sum, which is a sum of the detected transmission occupation period and the transmission occupation period corresponding to the transmission information, is shorter than a predetermined allowable period based on a performance of the bus. The transmission controlling process transmits the transmission information onto the bus, if the use channel is not used by the post-initialization information and further the occupation period sum is shorter than the predetermined allowable time, in accordance with a judgment result of the channel judging process and a judgment result of the occupied period judging process.
According to this aspect, in the same manner as the above described one aspect of the information transmitting/receiving apparatus of the present invention, it is possible to prevent a plurality of different transmission informations from being mixed on one channel, and can also prevent a transmission occupied period out of the standard from being generated.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings briefly described below.